Photoacoustic tomography imaging based on an acoustic lens imaging system

Photoacoustic tomography is a new type of medical imaging technology based on the measurement of laser-induced ultrasonic waves. It can detect the light absorption distribution of the target hidden inside optically turbid or opaque tissues. When a short laser pulse illuminates the scattering medium, such as biological tissue, the scattering media will generate ultrasound signals which are linearly proportional to the optical absorption of the media. The ultrasound signals are imaged with an acoustic lens. According to the imaging principle of lens, the photoacoustic signals from a plane in scattering media require the same delay time to reach the image plane, and the signals from different planes require different delay time to reach the same detecting plane. A BOXCAR was used to hold on the same delay-time, and a 64-element linear transducer array was one-dimensionally scanned on an imaging plane to acquire the acoustic pressure distribution, and the signals were recorded and reconstructed by a computer. By scanning the sampling gate of BOXCAR, the photoacoustic images of different planes in the media can be obtained. We experimentally obtained photoacoustic tomography images on different planes of the scattering media successfully. The images are vivid and contrast clearly with the background. This method directly provides images of absorbing structures without the need of computational reconstruction.